A while ago there was a framework Blobs for building box-connector
diagram editors.
It is probably a somewhat bit-rotted now:
http://www.cs.york.ac.uk/fp/darcs/Blobs/
I seem to remember a Haskell Workshop report about Dazzle (the
application that was the genesis of Blobs) but it doesn't appear t
I am designing some graphical editor ( visio - dia like) and would be
interested to hear any pointer to help me think on the architecture of this, in
term of data structure/ EDSL/ persistence/ paradigm (FP/ FRP/...)
for the different "layers of abstraction " I may see , like
rendering libraries
